1. Technical Field
The present invention relates in general to a method and apparatus for controlling computers remotely. The invention more particularly relates to a computer being controlled remotely by an operator terminal via a high speed fiber-optic transmission line.
2. Background Art
In many applications, data security for computers is of paramount importance. For example, computers used on factory floors, hospitals, financial institutions, public venues, refineries and other such applications oftentimes present issues relating to the security of the data being processed. Also, the environment may not be suitable for the use of the computers where it may be difficult or impossible to maintain a proper operating environment relative to temperature and humidity.
Therefore, it has been proposed to have the computer disposed in a safe and controlled environment, and have one or more operator terminals located remotely from the computer at a position where the user can enter and receive information interactively with the computer. In this regard, the computer can then be secured in a safe, air-conditioned location away from the environment where the operator terminal can still communicate with the computer.
There can be many applications where the operator terminal must be located at a great distance from the computer. For example, it may be desirable to have the operator terminal located at a position many kilometers apart from the computer. At such great distances, it becomes important to have a high speed transmission link such as a fiber-optic transmission line interconnect one or more of the operator terminals with the remotely located computer. High speed transmission links require a very stable (low jitter or phase noise reference clock.) As a result, such a system can be inherently unstable in its data transfer over the fiber-optic transmission line. More specifically, for example, if a 40 bit data word is used, an additional eight bits of link management and protocol information must be added to each data word, for a total of 48 bits. If the system is to operate at a 32.5 MHz clock speed, then the system must operate at 1.569 GHz (32.5 MHz times 48 bits). The period for such a rate would then be 0.637 Nano seconds. If the phase noise or jitter is equal to about one Nano seconds, the period for transmitting the information would actually be less than the period for the jitter, thereby resulting in a totally unacceptable and inherently unstable system.
Therefore, in order to have a long distance remotely controllable computer system over high speed fiber-optic transmission lines, it would be necessary to have a method and apparatus which would be able to transmit information in a highly stable and reliable manner.
Additionally, with such a remotely controllable system, it is also important that the system be highly reliable to maintain the integrity of the data. In this regard, special consideration must be made to ensure that the fiber-optic connection is "hot-pluggable." This means that the fiber-optic connection should be able to be disconnected from a failed or failing computer and then connected to a back-up computer without the need for rebooting either computer. This feature would also be useful when upgrading software and/or hardware. Similarly, it would be desirable to disconnect an operator terminal, or connect one to the transmission line without disrupting the operation of the computer. Additionally, especially where long distances are encountered, it would be desirable to prevent the computer from requiring rebooting should the fiber-optic transmission line be disrupted or severed inadvertently.
Thus, it would be highly desirable to have such a new and improved method and apparatus for controlling a computer remotely, even at long distances, while enabling either the computer or the operator terminal to be disconnected from the fiber-optic transmission line, or the transmission line becoming inadvertently disabled, without interrupting or otherwise disturbing the computer in a "hot pluggable" manner.